Original U.S. WWII USAAF Pilot Type C-1 Emergency Sustenance Vest - Unissued U.S. Equipment They are all roughly the

They are all roughly the same size

Probably dating to 1760-1800

a Pickelhaulbe style thick leather adjustable chin strap with securing rings to the inside of the helmet bowl

so this might have been intended for an installation where this functionality was disabled

Original U.S. WWII USAAF Pilot Type C-1 Emergency Sustenance Vest - Unissued U.S. Equipment They are all roughly theOriginal Item: Only One Available. The C1 survival vest was developed during World War two for use by the Army Airforce. The C1 vest has seen service by both Air force and navy personnel from World War Two through Korea and to a limited extent in Vietnam. The vest was made of dark olive colored green tackle twill and weighed 11 pounds when complete with survival contents. There were three large buttons on the front for closure. The vest was used alone